TOPIC:

Hi all
hope someone can answer this - I have a KZ440A from 1980 and I have an exhaust blow from the area of the balance pipe. 
I want it replace that area with some replacement steel tube but not sure if the balance pipe is necessary. If it is I’ll add it on but if not it will be easier to replace.

any ideas?

Simon  

I don't know, but on a 440 I would guess not. The 440B came stock w 2-into-1 muffler and the exhaust pipe diameter & muffler look about the same as a 2-2 system. However, it's possible the internal baffling is different, so the back pressure may not be the same. 
The crossover pipe adds some rigidity to the system. Some guys have used copper pipe & fittings to make a repair.

IMHO generally manufacturers don't do things for "fun". With separate carbs and dual exhausts what you basically have is 2 x 220cc single cylinder engines working together, you "sync" the carbs to balance the two sides so common sense says balancing the exhaust will also aid smooth running (why do Magniflo fit "X" pipes to all their V8 dual systems) In short will it run without? - yes it will. Will it run as smoothly as it does with? - probably not . This is just my opinion but I am sure if you google "exhaust balance pipes" you will get a very technical explanation
Exhaust H-Pipes vs. X-Pipes: What You Need to Know - YouTube

As I understand it, a crossover pipe can help the manufacturer shore up a soft spot in the torque curve, and can allow the use of more restrictive (quieter) mufflers by allowing each cylinder to exhaust through both mufflers. Is the difference large? I doubt it, but then with a 440, you are not starting with a ton of power.

it may be a fairly simple repair, depending on exactly where the leak is.

I was thinking the KZ400 isn't a high performance motorcycle, so try it without the crossover & see how it runs. It might be pretty obvious if it's not up to snuff.  Check the spark plugs before doing anything, then after. and keep an eye on them for x number of miles.  Also do basic tuneup type maintenance, such as checking/lubricating the timing advancer.  In the mean time I would keep an eye out for a good set of mufflers. NOS can be pricy but possibly worth it if not too expensive.  

ps: the KZ400 doesn't have a lot of horsepower & modifying the exhaust might loose a precious few.